// 跳轉到指定高度
scrollTo (num) {
      let speed = Math.floor((num-this.arriveTop) / 30)
      let timer = setInterval(() => {
        this.arriveTop += speed
        // 判定現(xiàn)在是否小于分出的大小
        if(Math.abs(this.arriveTop-num)<Math.abs(speed)){
          this.arriveTop = num
        }
        document.documentElement.scrollTop = document.body.scrollTop = this.arriveTop
        if (this.arriveTop === num) {
          clearInterval(timer)
        }
      }, 10)
    }
// 監(jiān)聽dom滾動事件
    onScroll () {
      this.arriveTop = window.pageYOffset || document.documentElement.scrollTop || document.body.scrollTop
      // 識別關于我們，判定頭部以及返回嘔吐不按鈕的顯隱
      const info = document.querySelector('.info').offsetTop-40
      this.isActive=this.arriveTop>=info?true:false
      // 記錄大事件和媒體報道的頭部
      const offsetTop1 = document.querySelector('.section2').offsetTop-40,
            offsetTop2 = document.querySelector('.mtport').offsetTop-80
      switch(true){
        case this.arriveTop<offsetTop1:this.showIndex=0;break;
        case this.arriveTop<offsetTop2:this.showIndex=1;break;
        default:this.showIndex=2;
      }
    },

END...